Biological marker studies in schizophrenia: 1. Cytogenetic evaluations: No abnormal chromosomal patterns (including fragile-X) were noted in a study of approximately 40 males with schizophrenia. 2. Genetic Marker Studies: No association of Restriction Fragment Length Polymorphisms were found in genomic DNA from schizophrenics using Neuropeptide Y and somatostatin DNA probes. 3. Viral studies (herpes class, HTLV antibodies) were negative. Although approximately 1/3 of schizophrenic patients studied had elevated antibody titres to Epstein-Barr virus (EBV), siblings with schizophrenia were not concordant for seropositivity, and a hospital control population was similarly increased. Treatment of these elevated EBV antibody titre patients with acyclovir did not produce beneficial effects. 4. Computed tomography (CT): The finding reported by others of an association of small heads with schizophrenia was not confirmed by our CT measurements. Clinical study of schizophrenia sibs: A study of clinical variables in multiplex families with schizophrenia is in progress. Over 60 families with more than one schizophrenic sibling have been recruited from throughout the USA, and clinical evaluations have been completed on all. Analysis of the data is in progress. Initial examination reveals no concordance for characteristic clinical symptoms, a negative symptom syndrome or for schizoaffective diagnoses within sets of siblings.